The book is divided into three parts that are logically connected. The first part defines the principal characteristics of the subterranean world and describes the microorganisms that live there as well as the environmental constraints they are subjected to. The second part shows how the action of the microorganisms can modify the physico-chemical surroundings, the microbiological equilibria and the growth of plants. The third part dwells on a few methods of intervention that would help in limiting the proliferation of harmful microorganisms and how to make the best use of the activity of auxiliary microorganisms.

Part I: Inert Components; Living Components of the Soil; Biological Activity of the Soil; Effect of Environment on Microorganisms�Part II: Modifications of Physico-chemical Characteristics of the Environment due to the Effect of Microorganisms; Interactions between Microorganisms; Interactions between Microorganisms and Plants�Part III: Why Intervene?; Interventions against Unfavourable Organisms; Utilisation of Auxiliary Microorganism?; References